Daniel Samson
2719b93530
These were the awkward ones. Each began with an operation packed into a single byte — two of them with a version wedged in beside it — so there was no wrapping them: the layouts had to be rebuilt. The device manager's own enumerate and subscribe become the reserved verbs that mean the same thing everywhere, its replies lose three status structs the envelope already carries, and a device id becomes the packet's target. Power drops the version it repeated on every request, because describe is the handshake, and stops claiming a 64-byte ceiling it never needed for calls. USB moves a control transfer's data to the packet tail in both directions, which makes the status length the transferred length and retires a field that had been saying the same thing twice. The danger in this one was not the protocols but their readers. Init recognised a power button by two bytes at the head of a message, the ACPI service dispatched on the first byte, the xHCI driver read its operation with a raw integer load, and the HID drivers reinterpreted a report wholesale — none of which would have failed to compile once the layouts moved. They would simply have stopped: no shutdown on the power button, no reports from the keyboard. Every one of them now reads through the generated types, and the shutdown gate that answers only a subscriber is the same code it was. Two sizes were decided by measuring rather than assuming. The child-added message is both a request and the event broadcast to subscribers, and alignment rounds it to 48 bytes, which puts its packet exactly on the 64-byte push floor — a test pins that, because a field added carelessly would now overflow it. The interrupt report gives up eight bytes of inline room to make space for the header; the two drivers that produce reports send eight and four. Suite 110/110.
75 lines
4.0 KiB
Zig
75 lines
4.0 KiB
Zig
//! The "protocol" library domain: the wire protocols — each service's public
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//! interface, exposed as its own module (docs/driver-model.md). Both sides of
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//! every conversation depend on the contract by name; neither reaches into the
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//! other's files. Pure flat wire types: no protocol module imports anything.
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//!
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//! One module here is not a protocol but the shape the others are written in,
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//! and therefore the one module every other one imports:
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//!
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//! envelope : the packet prefix + comptime Define (docs/os-development/protocol-namespace.md)
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//!
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//! vfs-protocol : the VFS server <-> the file layer (unistd/stdio)
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//! input-protocol : the input fan-out service <-> sources + subscribers
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//! block-protocol : a filesystem <-> a block driver (usb-storage)
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//! usb-transfer-protocol : a USB class driver <-> the xHCI bus driver
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//! device-manager-protocol : the device manager <-> drivers + discovery
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//! display-protocol : the compositor's client-facing surface
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//! scanout-protocol : the compositor -> a native scanout driver (docs/display-v2.md)
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//! power-protocol : system power's domain-named surface (docs/power.md)
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const std = @import("std");
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pub fn build(b: *std.Build) void {
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// Not a protocol, hence not `-protocol`: the envelope is what a protocol is
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// defined *through*, so it is built first and handed to every protocol
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// below as their one import.
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const envelope = b.addModule("envelope", .{ .root_source_file = b.path("envelope/envelope.zig") });
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for ([_]struct { name: []const u8, root: []const u8 }{
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.{ .name = "vfs-protocol", .root = "vfs/vfs-protocol.zig" },
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.{ .name = "input-protocol", .root = "input/input-protocol.zig" },
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.{ .name = "block-protocol", .root = "block/block-protocol.zig" },
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.{ .name = "usb-transfer-protocol", .root = "usb-transfer/usb-transfer-protocol.zig" },
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.{ .name = "device-manager-protocol", .root = "device-manager/device-manager-protocol.zig" },
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.{ .name = "display-protocol", .root = "display/display-protocol.zig" },
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.{ .name = "scanout-protocol", .root = "scanout/scanout-protocol.zig" },
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.{ .name = "power-protocol", .root = "power/power-protocol.zig" },
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}) |protocol| {
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_ = b.addModule(protocol.name, .{
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.root_source_file = b.path(protocol.root),
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.imports = &.{.{ .name = "envelope", .module = envelope }},
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});
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}
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// Standalone `zig build test` for this domain alone; the root build keeps
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// its aggregate test step.
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const test_step = b.step("test", "Run the protocol unit tests");
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// The envelope tests itself with no import of its own — everything else
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// imports it, so it is built separately rather than importing itself.
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const envelope_tests = b.addTest(.{
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.root_module = b.createModule(.{
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.root_source_file = b.path("envelope/envelope.zig"), // framing round trips, verb numbering, dispatch, the floors
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.target = b.resolveTargetQuery(.{}),
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}),
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});
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test_step.dependOn(&b.addRunArtifact(envelope_tests).step);
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for ([_][]const u8{
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"vfs/vfs-protocol.zig", // NodeKind / DirectoryEntry sizes + op values
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"input/input-protocol.zig", // event numbering + the push-floor budget
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"display/display-protocol.zig", // pack(): native pixel encoding per format
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"device-manager/device-manager-protocol.zig", // the dual-use report, exactly on the push floor
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"power/power-protocol.zig", // the event kind as the packet's verb
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"usb-transfer/usb-transfer-protocol.zig", // the tail-carried control stage + the trimmed report
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}) |root| {
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const protocol_tests = b.addTest(.{
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.root_module = b.createModule(.{
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.root_source_file = b.path(root),
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.target = b.resolveTargetQuery(.{}),
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.imports = &.{.{ .name = "envelope", .module = envelope }},
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}),
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});
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test_step.dependOn(&b.addRunArtifact(protocol_tests).step);
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}
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}
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